Conventional urethane-type polymers are prepared by the reaction of a polyol or a polyol-based compound with an isocyanate, typically in the presence of a metallo catalyst, and a curing agent, such as an amine. Caprolactone-type polyol polymers have been suggested for reaction with aryl isocyanates in the presence of various metallic catalysts, such as organo metallic catalysts comprising tin, lead and zinc and combinations thereof. However, when these catalysts are employed with an aliphatic isocyanate, together with a caprolactone polyol, a very slow-curing polymer results. While various combinations of the metallic catalyst may vary and the curing time, such as the combination of both lead and tin, the reaction time to prepare the aliphatic isocyanate base polymers is still quite slow, typically 2 to 24 hours or more.
In the preparation of urethane polymers, aromatic diamines, such as Detda; that is, diethyl toluene diamine, have been found to provide fast reaction between polyols with only primary OH groups less than 1250 mw and aliphatic biuret or trimerized hexamethyl diisocyanates. However, the use of such Detda catalysts provides a discoloration problem, due to the oxidation of the Detda catalysts. The Detda-type catalysts oxidize on heat and on exposure to sunlight. While the use of the Detda provides initially for a clear polymer, the continued use of the catalyst provides for a discolored; that is, a slightly brown-colored, polymer, so that the color matching of the polymer must be done with each batch, in order to provide a reproducible polymer. Typically, as the oxidation process of the Detda polymer proceeds, the amount of pigment, such as a white pigment, required, to obtain the desired color match, changes, so that the amount of pigment may increase from two to ten times from that of the original Detda-type catalyst source, in order to obtain the ultimate result in color-matching polymer. While reaction times, employing the Detda-type catalysts, can be quite fast-reacting, as low as 10 to 15 seconds, with aliphatic isocyantes, when injecting into a reaction-injecting molding process; that is, a RIM process, or a spray applied in an open mold, based upon 140.degree. F. chemical temperatures, the color discoloration and variation of such polymers, based on Detda-type catalysts, create a considerable problem. White or light-colored polymeric parts account for a significant portion of the RIM and urethane market, and, therefore, Detda-type catalysts are often not practical, such as in applications where color reproduction is important.
Therefore, there exists a need to provide for aliphatic isocyanate base polymers which are fast-reacting and which have good color stability, so as to provide good and reproducible color-matching properties, and which polymers may be employed within a RIM process and in spray processes and applied as various gel coats or in open-molding processes, and which polymers have high tear, tensile and green strength.